1. Field of the Invention
The present invention relates to mat members, an exhaust gas treating apparatus, and a silencing device.
2. Discussion of the Background
The number of automobiles has been rapidly increasing since the beginning of this century. Accordingly, the amount of exhaust gas discharged from internal combustion engines of automobiles has also been rapidly increasing. Particularly, various substances included in exhaust gas from diesel engines cause pollution, and thus have an increasingly serious impact on the global environment today.
Under such circumstances, various exhaust gas treating apparatuses have been proposed and put into practice. In a typical exhaust gas treating apparatus, a cylindrical member (casing) is provided in the middle of an exhaust pipe connected to an exhaust gas manifold of an engine. Inside the casing, there is an exhaust gas treating body with opening faces corresponding to the inlet and the outlet for exhaust gas, which exhaust gas treating body includes multiple microscopic cavities. Examples of the exhaust gas treating body are a catalyst carrier and an exhaust gas filter such as a diesel particulate filter (DPF). In the case of a DPF, due to the above structure, as the exhaust gas is discharged through the inlet opening face and the outlet opening face of the exhaust gas treating body, particulates are trapped in the walls around the cavities. Thus, the particulates can be removed from the exhaust gas.
A holding seal member is typically provided between the exhaust gas treating body and the casing. The holding seal member prevents the exhaust gas treating body from breaking as a result of contacting the casing, which may occur while a vehicle is traveling. The holding seal member also prevents exhaust gas from leaking through a gap between the casing and the exhaust gas treating body. The holding seal member also prevents the exhaust gas treating body from being disengaged due to exhaust gas pressure. Furthermore, the exhaust gas treating body needs to be maintained at high temperature in order to maintain reactivity, and therefore the holding seal member is required to have heat insulation properties. In order to satisfy such requirements, there are mat members made of inorganic fiber such as alumina fiber.
The mat member is wound around at least a part of the peripheral surface of the exhaust gas treating body excluding the opening faces, and is integrally fixed to the exhaust gas treating body with the use of taping or the like, thereby functioning as a holding seal member. Then, this integrated component is press-fitted inside the casing, thereby configuring an exhaust gas treating apparatus.
The mat member includes multiple microscopic inorganic fibers (usually having a diameter of 3 μm through 8 μm). Such inorganic fibers frequently foul the operational environment. For example, while an operator is handling the mat member, the inorganic fibers become detached from the mat member and scatter around the surrounding environment.
In order to reduce inorganic fibers that scatter while the mat member is being handled, there have been technologies proposed for providing films made of high polymer resin on the front and back sides of the mat member (see patent Japanese Laid-Open Patent Application No. H8-61054 and Japanese Laid-Open Patent Application No. 2003-293756).
The contents of Japanese Laid-Open Patent Application No. H8-61054 and Japanese Laid-Open Patent Application No. 2003-293756 are incorporated herein by reference in their entirety.